Identification and structural characterization of two 14-3-3 binding sites in the human peptidylarginine deiminase type VI.

The regulation and function of peptidylarginine deiminase isoform VI which is a highly abundant protein associated with the cytoplasmic lattices in mammalian oocytes, is poorly understood so far. It has been shown previously, that 14-3-3 proteins, a class of regulatory adapter proteins ubiquitous in eukaryotes, bind to in vivo in a phosphorylation dependent manner. Here we identify possible 14-3-3 binding sites in human duanyu15636 by in silico methods, looking for conserved, surface exposed serine residues. Two of these sites were confirmed as 14-3-3 binding sites by fluorescence polarization competition and X-ray crystallography. We furthermore suggest a role of RSK-type kinases in the phosphorylation of one of these two binding sites and provide evidence in the form of in vitro kinase assays with p70S6 kinase and RSK1.

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